Host-associated biofilm formation and dispersal mechanisms

摘要 细菌可以形成多细胞群落，其中单个细胞受到环境保护， 例如抗生素，由于被包裹在由多糖组成的保护性基质中 和其他大分子，[2]在生理上不同于自由生活的细胞。生物膜形成 增强了细菌在表面，包括宿主组织和非生物表面，如医疗表面， 植入物，并通过扩散过程在远端位置播种随后的感染。由于这些 由于生物膜的特性，生物膜中的细菌是大多数医院获得性感染的原因，因此， 理解生物膜如何形成和从这种生物膜中分散是至关重要的。虽然许多动物 虽然已经开发了生物膜形成的模型，但是很少（如果有的话）允许目视检查生物膜形成 和扩散事件以及随后的殖民结果的定量分析。一个如此强大的 然而，可以在费氏弧菌-鱿鱼（Euprymna squidopes）共生中找到模式。为了殖民，V。 费氏杆菌首先在共生器官的表面形成生物膜，然后从其分散进入， 最终定植在该器官深处的位点。我们的工作表明，生物膜形成所需的基因 在实验室培养物中，宿主相关（HA）生物膜和定殖同样需要，而遗传 在实验室中增强生物膜形成的变化也显著地增强HA生物膜和定殖。这 强烈的相关性为我们提供了一个特殊的机会来发展和测试有关机制的假设 HA-生物膜的扩散和随后的定殖。我们的工作揭示了HA生物膜和 定殖依赖于SYP，一个参与SYP多糖产生的18个基因位点，以及多个 传感器激酶和控制syp转录和转录后事件的反应调节剂。我们有 最近发现，钙（Ca 2+）和一氧化氮（NO）分别作为一种强诱导剂和抑制剂， 生物膜形成Ca 2+是一种生理相关的信号，似乎影响许多过程，但如何 它的作用尚不清楚。NO，它是由鱿鱼产生的，已知会影响HA-生物膜，可能 影响syp转录所需的传感器激酶之一，我们建议评估潜在的 机制等我们还准备鉴定促进/抑制HA生物膜的其他生理信号。我们 最近发现了在实验室培养中可以观察到扩散的条件， 观察到，V. fischeri在完全生长的培养物中经历了多轮的形成和传播，结果 这表明是由转录后机制控制的。我们已经开始调查这一过程， 确定一组参与控制传播的基因。我们建议发展一种机械的理解 这些扩散基因和控制扩散事件的因素，以及寻找其他我们认为 预测存在。我们预计，这项工作将提供深入了解的机制，细菌 对环境作出反应，并在动物宿主内的多细胞群落中进出。

Abstract Bacteria can form multi-cellular communities in which individual cells are protected from environmental insults such as antibiotics by virtue of being [1] encased in a protective matrix comprised of polysaccharides and other macromolecules and [2] physiologically distinct from free-living, planktonic cells. Biofilm formation enhances the ability of bacteria to colonize surfaces, including host tissues and abiotic surfaces such as medical implants, and seeds subsequent infections at distal locations through dispersal processes. As a result of these characteristics, bacteria in biofilms are responsible for the majority of hospital-acquired infections and thus understanding how biofilms form and disperse from such biofilms is critical. Although numerous animal models of biofilm formation have been developed, few, if any, permit visual examination of biofilm formation and dispersal events as well as a quantitative analysis of subsequent colonization outcomes. One such robust model, however, can be found in the Vibrio fischeri-squid (Euprymna scolopes) symbiosis. To colonize, V. fischeri first forms a biofilm on the surface of the symbiotic organ, then disperses from it to enter and ultimately colonize sites deep within this organ. Our work has shown that genes required for biofilm formation in laboratory culture are similarly required for host-associated (HA) biofilms and colonization, while genetic changes that enhance biofilm formation in the lab also strikingly enhance HA biofilms and colonization. This strong correlation affords us an exceptional opportunity to develop and test hypotheses about the mechanisms of HA-biofilms, dispersal and subsequent colonization. Our work has revealed that HA biofilms and colonization depend on syp, an 18-gene locus involved in production of SYP polysaccharide, and on multiple sensor kinases and response regulators that control syp transcription and post-transcriptional events. We have recently identified calcium (Ca2+) and nitric oxide (NO) as a strong inducer and inhibitor, respectively, of biofilm formation. Ca2+ is a physiologically relevant signal that appears to affect numerous processes, but how it does so is as-yet unknown. NO, which is produced by the squid and known to influence HA-biofilms, likely impacts one of the sensor kinases required for syp transcription, and we propose to evaluate the underlying mechanisms. We are also poised to identify other physiological signals that promote/inhibit HA biofilms. We have recently uncovered conditions in which dispersal can be visualized in laboratory culture, and have observed that V. fischeri undergoes multiple rounds of formation and dispersal in fully-grown cultures, a result that suggests control by post-transcriptional mechanisms. We have begun to investigate that process by identifying a set of genes involved in controlling dispersal. We propose to develop a mechanistic understanding of these dispersal genes and the factors that control dispersal events as well as to search for others that we predict to exist. We anticipate that this work will provide insights into the mechanisms by which bacteria respond to their environment and transition in and out of multi-cellular communities within an animal host.